1. Field of the Invention
The present invention relates to a camera having a photographing lens-driving device operated by the electromagnetic force for focusing and a driving device operated by the electromagnetic force for the control of an exposure amount.
2. Description of the Prior Art
As a method for moving the lens unit for focusing operation and others, in the past, there have been a method wherein a motor is used as a driving source and a method wherein an electromagnetic force is used as a driving source. The former further includes a method wherein the photographing lens, like the one used in a lens-shutter camera, is energized with a spring to the position of infinity when the film is wound up after the completion of photographing and then the photographing lens is drawn out for photographing by the motor up to the position required by a measured-distance signal and a method wherein the amount of rotation of the motor and the direction of rotation are changed by the measured-distance signal, as seen in the AF device of a single lens reflex camera, thereby the photographing lens is moved, both of which require the addition of gear reduction device and of a device that converts the revolving motion to the rectilinear motion and therefore it is becoming hard to incorporate the former into the latest camera that is moving toward a trend of small size and light weight.
In the case of the latter, due to the electromagnetic method, it is possible to totally control with the amount and direction of the current sent to the moving coil member and thereby it is possible to reduce the number of steps for the movement of the photographing lens and thereby to simplify the control circuit and the control mechanism, but in the case of the conventional electromagnetic device, a fixed permanent magnet and a moving coil member are arranged so that they face each other in a plane therefore the device for converting the revolving motion of the moving coil member to the rectilinear movement is still needed, which restricts the miniaturization of a camera. Further, like the conventional motor-driven mode, there still is applied a method wherein the photographing lens moves from the position corresponding to the infinity to the position corresponding to the close distance and thereby the great driving force is required. However, it is impossible to make the effective length of the coil long enough due to the necessity to provide at the center portion of the moving coil member the space necessary for the optical system and therefore the driving force is weak and the function thereof is insufficient.
In the case of the camera having the conventional electromagnetic driving device, the holding frame for the permanent magnet and the lens holder for the photographing lens are separate each other regardless of whether the electromagnetic driving device is for shutter-driving or for photographing lens-driving. The reason for that is because it has been considered to be advantageous, when the operation efficiency and the yield rate etc. are considered, to separate into units by function. Practically, however, movable parts are limited to the parts in very small number such as a moving coil member and others and therefore the adjustment work in assembling is unnecessary and it is presently less necessary to take the trouble to constitute each mechanism with a separate parts by function. Rather, the recent camera that is small in size and is of high capability, dividing the mechanism by functions thereof has led to disadvantages that the mounting accuracy is deteriorated and narrowed internal spaces can not effectively be used. Like an electromagnetic driving shutter means, for example, when the design is made with an optical axis of the photographing lens as a standard, if the holder ring for the photographing lens and the electromagnetic driving shutter means are separated each other by functions, eccentricity for mounting and an error for positioning etc. thereof tend to be produced and thereby the holder ring can not be used as it is as a bearing for the moving coil member of the electro-magnetic driving shutter and there has been a problem that an excessive space is required there. Further, in the case of a conventional between-lens-shutter camera, a front lens holder ring and a rear lens holder ring are connected through the supports of the shutter means or the like. Consequently, the following disadvantages have existed. Firstly, the supports or the like are needed to be provided at the location where the complicated shutter time adjusting mechanism and others are avoided and thereby the efficient parts layout is retarded and unnatural layout has been compelled, secondly, in order to avoid the supports of aforesaid shutter device and others, unnecessary connecting parts have been required for the connection between the mechanisms which are directly connectable in the shutter time adjusting mechanism, and thirdly, the number of the connecting points between the shutter base plate supporting the front lens holder ring as well as the shutter and the rear lens holder ring is increased and thereby the optical center tends to be deviated thus many highly accurate positioning parts have been required.
Such disadvantages adversely affect not only on the mechanism layout but also on the accuracy and cost and especially for the recent camera whose internal space is considerably limited due to the miniaturization, the disadvantages have created serious problems.
The present invention is intended to solve various problems mentioned above.